Internal combustion engines have developed into highly reliable prime movers for transportation as well as stationary applications. Engines based on the Otto cycle and the Diesel cycle have shown to be very durable, inexpensive to produce and until recently, inexpensive to operate. Until the 1973 oil shortage, the internal combustion engine was fueled almost exclusively by seemingly unlimited supplies of low cost petroleum derived fuel. This permitted the internal combustion engine to be made available in virtually any size with relatively high power output being obtained by increasing the amount of fuel input and cylinder displacement. This trend resulted in internal combustion engines which became increasingly wasteful from a thermodynamic standpoint. This increased waste of available British Thermal Units (B.T.U.'s) only began to gain significance when the cost of petroleum based fuels began to rise. Moreover, since the mid 1960's environmental concerns expressed by both the public and governmental agencies have resulted in increasingly stringent regulations on the amount of unburned hydrocarbons and oxides of nitrogen emitted by the typical internal combustion engine. Further, U.S. Government Corporate Average Fuel Economy (CAFE) regulations have required all automobile manufacturers to decrease average fuel usage of the typical automobile engine. Industry has responded to these regulations by adding to engines many complex and expensive methods to decrease average fuel usage and to reduce harmful emissions.
Primarily because of the foregoing, the automotive industry has found that it is no longer feasible to increase the cylinder size of the engine and fuel input in order to gain a desired power output, and attempts to solve the problem have resulted in a trade-off between additional fuel economy and lowered emissions. The net result has been a reduction in reserve horsepower available for many engine applications. Furthermore, the trend appeared to be toward increasingly complex and expensive methods of improving horsepower without an increase in fuel input.
Recently, however, efforts have been made to design engine systems which directly address the traditional thermodynamic inefficiency by utilizing the vast quantity of waste heat (up to 60% of available B.T.U.'s) normally dissipated to the environment to supplement the power output of the engine. At best, the mechanical power output of a conventional diesel cycle based engine is in the range of thirty to forty-two percent of the rate at which energy is released through the combustion of the fuel. The bulk of the remaining energy is lost to the environment through the exhaust gases and the engine jacket cooling system and its condenser. A system which can take lost heat and use it in the engine without great mechanical losses can double the power output or efficiency of a standard internal combustion engine. Examples of prior art systems which attempt to utilize this lost heat energy are Ridgeway U.S. Pat. No. 4,300,353, Eakman U.S. Pat. No. 4,366,674, and Kubo et al U.S. Pat. No. 4,901,531. Each of these patents, as well as other prior art teachings, attempt to redress the well-known thermodynamic losses through a recapture system. In such systems, the heat content of either the exhaust gases or engine coolant or both are used to vaporize a liquid which is then used to supplement engine output through various mechanical modifications to the engine system. All such systems, however, have one or more of the following disadvantages:
(a) The system is bulky and complex thereby adding significantly to the cost of the engine. PA1 (b) The system requires extensive modification of the normal internal combustion engine. For example, one or more of the engine cylinders are dedicated strictly for utilizing recaptured energy thereby reducing the engine output through normal combustion processes. PA1 (c) The system uses some type of turbine or supplemental drive train requiring reduction gears in order to add the recaptured power to the drive train, again adding significant cost and reducing the utility and reliability of the entire engine system. PA1 (d) At low engine output levels the heat content of exhaust gases is relatively low, and the amount of energy recaptured is therefore low and does not justify the use of a recapture system. Moreover, during these low output times the system components serve as a significant drag on the overall engine system.
Thus, it is an object of the present invention to provide an improved system for recovering and utilizing the heat energy produced during operation of the engine so as to supplement the engine output or reduce fuel consumption at a constant power output level.
It is a further object of the invention to provide an improved system for recovering and utilizing the heat energy produced during operation of the engine while leaving the engine unaltered and functioning in a normal manner at low power levels or when the recapture system is rendered nonfunctional by operator choice or system failure.
An additional object of the invention is to utilize an exhaust afterburner and regulated air fuel mixture in such a way to recover unburned chemical energy in the exhaust gases and substantially eliminate all combustible pollutants.